# Problem Running SH Plane-Wave Simulations **URL:** \ **Category:** SPECFEM\ **Tags:** specfem2d\ **Created:** [May 13, 2021, 4:59am UTC](https://community.geodynamics.org/t/problem-running-sh-plane-wave-simulations/1835 "2021-05-13T04:59:03Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Varun.Singla](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/varun.singla/32/783_2.png) [@Varun.Singla](https://community.geodynamics.org/u/Varun.Singla)\ **Post date:** [May 13, 2021, 4:59am UTC](https://community.geodynamics.org/t/problem-running-sh-plane-wave-simulations/1835/1 "2021-05-13T04:59:03Z")
Hi everyone! I would like to run **plane-wave** simulations of **SH waves** in SPECFEM2D. As mentioned in its user manual, I set ‘P\_SV’ and ‘initialfield’ parameters in DATA/Par\_file to ‘.false.’ and ‘.true.’ respectively. Further, I set ‘source\_type’ parameter in DATA/SOURCE to ‘2’ to select the case of S wave. However, when I run the solver, I get weird simulations that do not correspond to SH plane-waves. Can you please let me know where I am going wrong? You may note that when I set ‘P\_SV’ parameter (in DATA/Par\_file) to ‘.true.’ and the remaining parameters same as above, I am able to successfully simulate propagation of SV plane-waves. Thanks and Kind Regards, Varun Singla Research Scientist, School of Earth Sciences, University College Dublin ---
**Author:** ![dpeter](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/dpeter/32/227_2.png) [@dpeter](https://community.geodynamics.org/u/dpeter)\ **Post date:** [May 13, 2021, 4:33pm UTC](https://community.geodynamics.org/t/problem-running-sh-plane-wave-simulations/1835/2 "2021-05-13T16:33:23Z")
could you post your setup files (Par\_file, SOURCE) and the output to check? and how does it look when you would use source type 1 for your SH-wave simulations? ---
**Author:** ![Varun.Singla](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/varun.singla/32/783_2.png) [@Varun.Singla](https://community.geodynamics.org/u/Varun.Singla)\ **Post date:** [May 14, 2021, 6:25am UTC](https://community.geodynamics.org/t/problem-running-sh-plane-wave-simulations/1835/3 "2021-05-14T06:25:39Z")
> [@dpeter](#): > > could you post your setup files (Par\_file, SOURCE) and the output to check? Sure. Being a new user, however, I am unable to append these files here and have thus uploaded these on Gdrive: [Source\_type\_2\_files](https://drive.google.com/drive/folders/1sODVxSNd5jx0wsnIL3YJWUdXLetcFZjf?usp=sharing) This is a segment of the output that I get in the terminal: * * * Preparing initial field for plane wave source Implementing an analytical initial plane wave… \*\*\* calculation of the initial plane wave \*\*\* To change the initial plane wave, change source\_type in DATA/SOURCE and use: 1 or 4 - for a plane P wave 2 or 5 - for a plane SV wave 3 - for a Rayleigh wave 6 - for a mode initial displacement selected source\_type = 2 anglesource = 0.17453292519943295 initial SV wave of 10.000000000000000 degrees introduced. angle source = 0.17453292519943295 reflected convert plane wave angle: 22.459233779924258 mesh dimensions: x min/max = 0.00000000 5000.00000 z min/max = 0.00000000 5000.00000 Number of grid points = 160801 You can modify the location of the initial plane wave by changing xs and zs in DATA/SOURCE. for instance: xs= 2500.0000000000000 zs= 5000.0000000000000 (zs can/should be the height of the free surface) Max norm of initial elastic displacement = 2.00748444 Preparing source time function time stepping scheme: Newmark time stepping stages: 1 time step size : 1.00000005E-03 number of time steps: 3200 initital field : T Preparing image coloring allocating color image arrays locating all the pixels of color images total number of image pixels = 648830 done locating all the pixels of color images coloring image background based on vp done, preparation successful * * * The medium is homogeneous, elastic, and isotropic with width=height=8 km. Simulation is for right-travelling waves incident at an angle of 10 degrees. Ricker wavelet of frequency 6 Hz is chosen as source function. It appears from the above output that instead of incident SH plane-waves, SV plane-waves have been considered by SPECFEM2D. This is weird considering that I have set P\_SV=‘.false.’ in Par\_file. Below is a contour image of the displacements at an initial time-step, which also indicates that the case of an SH plane-wave has not been considered (there should be only 2 plane-waves: one incident and one reflected, whereas this image shows three). ![forward_image000000005](https://canada1.discourse-cdn.com/flex036/uploads/geodynamics/original/1X/adbf7b732e51fad10d151a76a5f3fdc8b7951015.jpeg) > [@dpeter](#): > > and how does it look when you would use source type 1 for your SH-wave simulations? It looks similar for source type 1, i.e., instead of incident plane SH waves, incident plane P waves are considered by SPECFEM2D. Weirdly enough, the output files correspond to displacement along only y-direction for both source type 1 and 2 (displacements for incident P and SV plane-waves should occur along x- and z-directions only). Much thanks for taking the time to go through my files! Varun